1. RIC 2009 Thermal Hydraulics & Severe Accident Code Development & Application Ghani Zigh USNRC 3/12/2009

2. 2 Thermal-Hydraulic and Ignition Phenomena Characterization of Prototypic Pressurized Water Reactor Assemblies

3. 3 Objectives  Provide prototypic thermal hydraulic and zirc-fire data for accident code validation under air flow conditions associated with: – Spent fuel pool complete LOCA Arrangement of high density fuel racks for mitigation strategy – Late phase core melt progression – Complete loss of water during refueling – Dry cask storage (thermal Hydraulic data  Data is needed to assess: – Cladding ballooning – Flow correlation (Pressure drop vs. Velocity) at low Re numbers – Initiation of zirc fire – Assess potential for propagation of “zirc fire” – Mitigation strategies concerning fuel assembly management  Pre-test (Blind) and Post test code to data comparison  BWR experiment and analysis is completed and will be available.

4. 4 Technical Motivation  Why not interpret BWR results for PWR ? – Geometry of PWR differs significantly from BWR  Previous BWR results not applicable – More rods, larger footprint – No water rods – No partial length rods  No Zr canister – Site specific storage cell defines annulus – May alter axial and radial burn front propagation – An analogous PWR study is required.

5. 5 Scope of Work  Full length 17×17 PWR Assemblies – Otherwise similar to BWR study  Phase 1 Testing – Single heated full length assembly Insulated “Hot neighbor” BC – Pre-ignition and ignition testing  Phase 2 Testing – Five (5) full length assemblies in 1×4 Center heated, peripheral unheated “Cold neighbor” BC Pressurized rods in two peripheral assemblies – Rod ballooning, requires design testing – Pre-ignition and ignition testing

6. 6 What is new and different?  Experience with the BWR project allowed to make improvements in the PWR experimental design – All full length PWR assemblies Commercially available 10.72 mm (0.422 in.) ZIRLO rods can be made into 9.52 mm (0.375 in.) heaters All assemblies naturally draft in 1×4 experiments  No complex flow and temperature control required – Fully prototypic peripheral assemblies in 1×4 experiments Allows pressurization of peripheral rods  Ballooning

7. 7 Fuel MgO PWR Testing (Technical Summary) Bottom end plug Top end plug with gas fill hole Zircaloy tube High density MgO ceramic 05001000 Temp (K)  C p (J/m 3 /K) Ballooning Design Electrically heated center assembly Unheated peripheral assemblies Prototypic 3×3 pool rack Ballooning peripheral assembly Phase 2 1×4 Full Length Insulation Hot wire Flow meters Thermo- couple Light pipe Hot wire Flow meter Storage cell Phase 1 Single Full Length 1500

8. 8 Proposed Testing Program for PWR 17x17 = Completed DescriptionPurposeAssemblyRod material Ballooning rod design Test pressurized rod performance, preliminary data on ballooning as function of initial internal pressure Single rodZircaloy Separate Effects Hydraulics – Determine form loss and laminar friction coefficients Single Prototypic Stainless Steel Pre-Ignition Thermal hydraulics – Determine temperature profiles and induced convective flow Single Prototypic Zircaloy Ignition Axial Ignition – Temp profiles, induced flow, axial O 2 profile, nature of fire Single Prototypic Zircaloy Pre-ignition Thermal radiation coupling and induced convective cooling in a 1  4 arrangement 1×4 Prototypic Zircaloy Ignition with ballooning Radial fire propagation and effect of fuel rod ballooning 1×4 Prototypic Zircaloy 1x4

9. 9 Phase 1: Axial Heating and Burn Propagation  Insulated “Hot neighbor” Boundary  Test Assembly – Single Westinghouse 17×17 RFA PWR skeleton – 9.52 mm (0.375 in.) electric heater rods made from 10.72 mm (0.422 in.) ZIRLO tube Same heater design as in BWR study  Pre-ignition Tests – Analogous to BWR testing except: Two storage cell sizes  Ignition Test – Similar to BWR burn except: Lack of channel box may alter axial propagation  O2 bypass more likely

10. 10 Proposed Testing Program for PWR 17x17 = Completed DescriptionPurposeAssemblyRod material Ballooning rod design Test pressurized rod performance, preliminary data on ballooning as function of initial internal pressure Single rodZircaloy Separate Effects Hydraulics – Determine form loss and laminar friction coefficients Single Prototypic Stainless Steel Pre-Ignition Thermal hydraulics – Determine temperature profiles and induced convective flow Single Prototypic Zircaloy Ignition Axial Ignition – Temp profiles, induced flow, axial O 2 profile, nature of fire Single Prototypic Zircaloy Pre-ignition Thermal radiation coupling and induced convective cooling in a 1  4 arrangement 1×4 Prototypic Zircaloy Ignition with ballooning Radial fire propagation and effect of fuel rod ballooning 1×4 Prototypic Zircaloy 1x4

11. 11 Phase 2: Radial Heating and Burn Propagation  “Cold Neighbor” Boundary  Test Assembly – 5 full length assemblies in 1×4 arrangement Center heated, peripheral unheated – Two peripheral assemblies with all pressurized rods Strain gauges on some rods  Provide internal pressure indication – Single prototypic 3×3 pool cell  Pre-ignition Tests – Analogous to BWR testing Natural draft flow in peripherals  Ignition Test – Effect of ballooning Indicated by induced flow in peripheral assemblies Pressure relief indicated by strain gauges

12. 12 Proposed Testing Program for PWR 17x17 = Completed DescriptionPurposeAssemblyRod material Ballooning rod design Test pressurized rod performance, preliminary data on ballooning as function of initial internal pressure Single rodZircaloy Separate Effects Hydraulics – Determine form loss and laminar friction coefficients Single Prototypic Stainless Steel Pre-Ignition Thermal hydraulics – Determine temperature profiles and induced convective flow Single Prototypic Zircaloy Ignition Axial Ignition – Temp profiles, induced flow, axial O 2 profile, nature of fire Single Prototypic Zircaloy Pre-ignition Thermal radiation coupling and induced convective cooling in a 1  4 arrangement 1×4 Prototypic Zircaloy Ignition with ballooning Radial fire propagation and effect of fuel rod ballooning 1×4 Prototypic Zircaloy 1x4

13. 13 Ballooning Rod Design  Prototypic Components – 9.50 mm (0.374 in.) ZIRLO tubing, Zr-4 end plugs and stainless springs Welding and helium backfill by Westinghouse Inc. – High density MgO ceramic pellets Same length and OD as UO2 pellets Hole in center sized so thermal mass matches spent fuel  3.2 mm (0.126 in.) hole

14. 14 Ballooning Rod Performance Testing  Single rods tests in tube furnace  Rods with solid MgO pellets for baseline – Excessive thermal mass – Sized for correct gas volume – 1.72, 2.07, and 2.41 MPa He  Rods with hollow MgO pellets – Correct thermal mass – Increased gas volume – Find pressure that best represents baseline

15. 15 Numerical Support  Main objective of project to provide prototypic data for code validation  Three component numerical effort – Experimental design – Pre-test predictions – Post-test analysis  Data available to all project participants – Test plans – Spreadsheet data files – Modeling database

16. 16 Summary  BWR ignition testing completed for over 3 years – Testing prototypic hardware vital Eliminate scaling arguments Represents fuel design intricacies – Established experimental expertise and nuclear vendor relationships  Significant differences between PWR and BWR assemblies – 264 PWR fuel rods vs 74 BWR fuel rods, – 11 PWR spacers vs 7 BWR spacers – No canister on PWR  PWR ignition testing proposed over 3 years – Improved cost effectiveness Personnel, testing capabilities and facilities well suited for proposed testing – All full length assemblies – Includes ballooning In unheated peripheral assemblies